Determined products, such as certain food products, have to be submitted to a hermetic storage for long periods of shelf life until the first opening and provided with a clear visual indication to the consumer that the package in which they are presented to the market has not been violated. Considering that many of these products are of progressive consumption, it is indispensable that, upon the first opening of the package, the lid which gives access to the interior of the can be closed again as many times as necessary during the progressive consumption of the stored product, in order to guarantee the tightness of the re-closed can and protect the remainder of the content thereof.
There are well known in the art the cans provided with a press-fit lid, which is fitted, by pressure, in a peripheral structural ring, internal to the upper edge of the body of the can and defining an annular upper wall for the latter. The tightness of the content is guaranteed, in this type of construction, by the lid fitting in the seating and retention seat, which can be provided in the structural ring that defines the annular upper wall of the can or in the tubular body of the latter.
In this type of closure it is desirable to obtain a high degree of tightness for long periods of shelf life, until the first opening of the container, and also thereafter, upon the subsequent closings of the lid during the progressive consumption of the packaged product. Moreover, it is also necessary that the opening and closing operations of the container are easy and safe, preventing injuries in the fingers of the user and also an involuntary and uncontrolled release of the product due to a sudden removal of the lid.
The Brazilian patent PI 0203950-8 of the same applicant proposes a closure arrangement for containers of the type considered herein, using a plastic lid comprising a sealing portion to be removably seated in the seat of the container and provided with an upper edge projecting radially to the outside of the seat, to be incorporated, by means of breakable bridges, to a seal portion carrying a lower skirt which is seated around the upper end of the container and which presents an interruption in which is positioned a gripping tab projecting downwardly from the sealing portion to which it is radially incorporated. The gripping tab can only be operated upwardly for removing the lid after breaking part of the seal portion and the breakable bridges, said seal portion being configured to cover the gripping handle. This prior construction of the same applicant is particularly directed to the tamper evident seal, the tightness of the lid being object of a constructive arrangement described and claimed in the Brazilian patent 9408643-5 (U.S. Pat. No. 5,899,352 and EP 0 706 486) and also in the Brazilian patent application PI 0203950-8 (PCT/BR03/00030), of the same applicant, according to which a circumferential groove, externally provided on a lateral peripheral wall of the lid and having a cross section in the form of an arc of a circle or a concave arc, is seated onto a circumferential rib, having a cross section in the form of an arc of a circle or a convex arc, formed in the annular upper wall of the container and defining the upper opening of the latter. The circumferential groove of the lid and the circumferential rib of the annular upper wall are configured to provide not only a safe axial retention of the lid on the container, but also a high degree of tightness of the closure.
However, the degree of tightness provided by this closure arrangement of the prior art does not guarantee the tightness required for storing certain products, as is the case of certain food products that require long shelf lives, without contamination of the interior of the container through penetration of contaminants or reduced amounts of oxygen from the ambient air.
This prior art closure arrangement allows easy and safe operations of opening and closing the lid, without the need of auxiliary tools, providing a reliable tamper evidence by the seal portion and also an adequate degree of tightness for the packaging of several products during the shelf lives thereof and, particularly, upon the closing of the lid after the first opening, during the progressive consumption of the packaged product.
However, despite all the positive features mentioned above, said closure arrangement object of PI 0203950-8 allows further improvements directed to a higher degree of tightness during the period of shelf storage, without impairing or harming the reopening and closing operations of the lid.